MAZDA6. KEY PRESS BUZZER.
If you don’t like the sound of a key press confirmation (buzzer) on the console panel or steering wheel, you can turn it off:
1. turn off the radio
2. press and hold the "seek" button down
3. press and hold the “5” button until the confirmation signal
Note: this cheat does not work on cars with a Bose sound system!

What are hidden button combinations?
On your stereo, bose and non-bose, you can press different combinations of two buttons to turn various functions on or off, or test certain aspects of the stereo system.

Why should you bother with some hidden features?
Aren't you tired of the beeping sound every time you press a button? It infuriates me that when I switch between stations or tunes on the disc to find a good song, I always hear this - “beep beep beep beep beep beep beep beep beep beep.”

Is this a complete list of hidden features?
No, and you can be sure that someday, someone bored in their Mac for a couple of hours and pressing buttons will find them. (or he will kidnap the engineer and torture him until he tells us all the secrets)

Do these features work for both bose and non-bose systems?
Yes and no. You can check the hidden button combinations on both systems, and you may see a message on the display that suggests it works for you, but there are certain functions that will work as shown on the display "only" on a certain system (see combinations below, if it works on both systems then I'll mark it as "both")

What can you do to help?
Well, if you're as bored as I am today, then go sit in your car and start pushing some buttons. If you find some combination or function that is not described here, in any case, post it here.

How to exit function change mode.
Some feature messages do not disappear from the screen. If this is the case, then simply press the stereo power off button, and then turn the power back on, but remember what options you changed, because the option will remain changed until you change it with the same button combination.

Display check:
Turn on stereo – Hold Power button + Seek Up button
Both: Backlight diagnostics of all icons on the display to check for dead or dim areas

Checking audio channels:
Turn on stereo – Hold Power button + Auto M Down button
Both: Diagnoses the health of audio channels in a specified order to determine the status of the speakers and the pairing between the head unit and each speaker.
1. Left door speaker and buzzer
2. Right door speaker and buzzer
3. Right rear door speaker and subwoofer
4. Left rear door speaker and subwoofer

Resetting stereo settings:
Turn on the stereo – Hold the Tune/Settings + button (any other button except the stereo power button)
Both: This will reset all system audio settings bass/treble/mid/fade... to factory settings. (but will not reset the station memory)

Checking the radio signal strength:
Turn on the stereo – Hold the power button + “2” button
Both: The combination allows you to display the signal strength of the radio wave or the status of the antenna or radio and antenna mount
(displays S-METER and numbers from 0 (worst) to 9 (best))

Antenna off/on:
Turn on the stereo – Hold the power button + AM button
Not BOSE: has no effect
BOSE: ???
(I think this is just a status display. When the system plays a CD, it is turned off, when the radio is on. Any other information is welcome)

Amplifier off/on:
Turn on the stereo – Hold the power button + “Scan Up” button
Both: Diagnose the performance of the amplifier's audio output channel to determine the status of the amplifier and the interface between the head unit and the amplifier.

Checking the buttons:
Turn on the stereo – Hold the power button + “MD/Tape” button
Both: This option allows you to ensure that all system buttons are operational. All buttons will emit an audio signal when pressed, even the buttons on the steering wheel.

Self-diagnosis - (the wiring has failed, I still need to check this function again):
Turn on the stereo – Hold the power button + AM button + “MD/Tape” button
Both: Step by step check proper operation of the audio system. The first message displayed is who made your head unit and the number. To stop diagnostics, turn the ignition key to the LOCK position

If anyone has cheats for Mazda, write to me.
I will definitely post them on this page with a link to the person who sent them!